The present invention relates to a radiation thermometer for measuring body temperature of a living body by detecting an amount of the infrared rays radiated from inside of an ear canal.
Radiation thermometers for use as the clinical thermometers have been heretofore available, with which an amount of the infrared rays radiated from inside of an ear canal is detected at noncontact, and converted into body temperature. An advantage of these radiation thermometers is that they can take the measurement in a short period of time as compared to the contact type thermometers utilizing mercury and thermocouples.
As an ordinary example, the radiation thermometer of this type shown in Japanese Patent Laid-Open Publication, No. H06-165 will be described hereinafter by referring to FIG. 27. As shown in FIG. 27, the radiation thermometer comprises a probe 1, a waveguide 2 extending within the probe 1 in a longitudinal direction, an infrared-ray-receiving element 3 for converting a radiant intensity of the infrared rays traveled through the waveguide 2 into an electric signal, and a signal processor 4 for measuring temperature from the converted electric signal.
By inserting the probe 1 into an external auditory canal (xe2x80x9cear canalxe2x80x9d), the infrared-ray-receiving element 3 receives the infrared rays radiated from the tympanic membrane (xe2x80x9ceardrumxe2x80x9d) and/or vicinity of it, and outputs an electric signal corresponding to an amount of the received infrared rays. Then, the signal processor 4 calculates a temperature of the eardrum and/or its vicinity from the electric signal.
Generally, the infrared-ray-receiving element 3 outputs an electric signal that corresponds to an aggregate amount of the infrared rays incident on it from all directions, and the waveguide 2 is made of a metal or processed with plating or the like on its at least inner surface so as to maintain a high reflectivity. The infrared rays radiated from the eardrum and/or vicinity of it reach the infrared-ray-receiving element 3 directly or by being reflected repetitively off the inner surface of the waveguide 2 of the foregoing structure. On the other hand, undesired infrared rays radiated from an inner surface, etc. of the probe 1 do not reach the infrared-ray-receiving element 3.
However, the incident rays reflected repetitively suffer a reflection loss equal to the reflection factor raised to the n-th power, since it is unfeasible to make the inner surface of the waveguide 2 a perfect reflecting body (the reflection factor of 1). Also, the light reflected at a low angle for a single reflection generally gains a lower reflectivity than the perpendicular light, thus resulting in a reflection loss. Since an amount corresponding to these reflection losses enters into the infrared-ray-receiving element 3 as a part of the infrared radiation emitted from the waveguide 2, an accurate measurement of the body temperature can not be attained because the infrared-ray-receiving element 3 is influenced by it, if temperature of the waveguide 2 changes when the probe 1 is inserted into the ear canal.
In order to avoid the above problem, the foregoing example of the prior art alleviates the temperature changes of the waveguide 2 by tapering off to a tip from a main base of the probe 1 so as to reduce likeliness of contact with the ear canal. Also, an example shown in Japanese Patent Laid-Open Publication, No. H05-45229, adopts a design in that a probe is constructed of a thermal insulation material on its surface, and of a thermally high conductive material in the core, so that it averts an influence of heat from the ear canal, and offsets the influence by quickly transmitting the heat it receives to an infrared-ray-receiving element. Furthermore, still another example shown in Japanese Patent Laid-Open Publication, No. H08-126615 adopts an idea that a probe is detachable, so as to eliminate an influence of heat retained in the probe by replacing it after each measurement.
However, none of the foregoing techniques are flawless for accurately measuring temperature of the eardrum and/or vicinity of it by eliminating an influence of the heat conducted from the ear canal to the waveguide, and they all have a problem of lacking accuracy in measuring body temperature due to the influence of temperature changes of the waveguide. In particular, there is a problem that measured temperature gradually shifts even for one and the same measuring subject, when the measurements are made repeatedly at short intervals, because of an influence of the waveguide as its temperature gradually changes.
If a thermally high conductive material is used for the waveguide in order to avert the effect of measuring errors caused by the aforementioned problem, a new problem arises in that the waveguide becomes liable to produce condensation on the inner surface at low temperature environment. This is because temperature of the metal surface does not rise readily at the low temperature environment, even when it comes in contact with air near a body temperature by being inserted into the ear canal. Hence, the condensation occurs on the metal surface, as the air containing moisture is chilled by the metal in a temperature below dew point. If a phenomenon of the condensation occurs on a component such as the waveguide having a function of reflecting the infrared rays, a measuring error can result because the infrared rays reaching the infrared-ray-receiving element is substantially reduced due to absorption and dispersion of the infrared rays by the condensation.
It is a common practice to use a sanitary cover on the probe when inserting a radiation thermometer into the ear canal, and the cover is discarded when removed after each use for the sake of sanitary protection, in the case the radiation thermometer is used for many and unspecified persons. Such a sanitary cover shall conceal a part contacting the tip of the probe with a membrane. This is because a tip of the waveguide extends to the tip of the probe, so that the tip shall be provided with the membrane in order to prevent dirt from adhering to the waveguide.
On the one hand, the sanitary cover is not necessary, and waste of resources by discarding them is avoidable, if subjects to be measured are limited to a few and specific persons such as those in a family or in an office of a small number of people, since spread of disease via the ear can be prevented by assigning a separate probe for each person. Even in the above case, however, the tip of the probe needs to be covered with a membrane made of an infrared transparent material in order to avoid dirt from adhering to the waveguide.
In any case, what is measured is an amount of the infrared rays passed through the membrane provided on the tip of the probe for the purpose of sanitation. It is not feasible to let the infrared rays pass through completely, since there is a component in the infrared rays that is absorbed and/or reflected when they pass through the membrane. Because a transmission factor of the infrared rays through the membrane disperses depending on thickness, etc. of the membrane, it raises a problem of causing an error in temperature due to the dispersion in the transmission factor when a new membrane is replaced, even if the thermometer is adjusted in advance with a specific membrane.
Announcing a measured temperature with voice can provide a good advantage, as the measured result is readily known when the thermometer is used by a blind person, or when measured in the dark. For example, one of the known methods is shown in Japanese Patent Laid-Open Publication, No. H06-142061.
However, it takes 2 to 3 seconds in order to announce the temperature vocally, while only 0.1 to 0.2 second suffices to notify a completion of the measurement with a beeping sound. In other words, temperature of the waveguide changes due to conduction of heat from the ear while the probe is kept inserted in the ear until the announcement ends, if a radiation thermometer of the foregoing structure makes an audible announcement. If the measurements are made repeatedly, it results in a problem that the temperature change of the waveguide during the announcing time causes a measuring error in the subsequent measurement, although it is not a problem if only one measurement is made.
On the other hand, if an infrared-ray-receiving element of a pyroelectric type is used, there arises a problem as follows. In general, two types of the infrared-ray-receiving element are commonly available, i.e. the pyroelectric type, whose output has a correlation to temperature change of the subject being measured, and a radiation thermopile type, which has a correlation with a temperature difference between the element itself and the subject. If an infrared-ray-receiving element of the pyroelectric type is used for measuring temperature of an object, such as the eardrum that has a steady temperature and constantly emits an invariant amount of the infrared rays, as a subject to be measured, it is necessary to forcibly change the infrared rays incident on it. A chopper is provided for this purpose in order to switch the infrared rays incident upon the infrared-ray-receiving element of the pyroelectric type between a light-admitting mode and a light-blocking mode. The chopper is constructed of a material that does not pass the infrared rays, such as a metal plate for example. As one of the methods, one end of the chopper is attached to a rotary shaft of a D.C. motor or an A.C. motor, and it is rotatory driven, so as to repeatedly interrupt the infrared rays through the infrared-ray-receiving element, between the light-admitting mode and the light-blocking mode. That is, the infrared rays incident upon the infrared-ray-receiving element 3 is interrupted by rotatory driving the chopper 5 of a semicircular shape attached to a rotary shaft of the D.C. or A.C. motor 6 in a direction of an arrow as shown in FIG. 28.
There is also another method for interrupting the infrared rays by repeating a forward and a reverse rotations within a predetermined angle with a pulse motor as a rotational driving source, as it is supplied with pulse waves at predetermined intervals. Referring to FIG. 29, one example of a temperature measuring apparatus shown in Japanese Patent Laid-Open Publication, No. H07-280652 is described hereinafter. A chopper 5 is driven for reciprocal motion by a crystal clock movement 7, which is a driving source operated in the same principle as the pulse motor, and interrupts the infrared rays through an infrared-ray-receiving element 3. The crystal clock movement 7 includes a permanent magnet 8, a core 9 and a coil 10, and the permanent magnet 8 connects to one end of the chopper 5. The coil 10 receives a pulse input through a first input terminal 11 and a second input terminal 12, and the permanent magnet 8 rotates in response to the pulse input, which in turn moves the chopper 5 reciprocally as shown by an arrow.
However, the foregoing example of the prior art for rotating the chopper by a driving source of the D.C. motor has a problem of low accuracy in the measured temperature due to dispersion of the light-admitting time and the light-blocking time. The D.C. motor normally varies its rotational speed due to fluctuation of the supply voltage etc. If the rotational speed varies, the light-admitting and the light-blocking intervals change, and this change of the intervals causes an output of the infrared-ray-receiving element 3 to vary, thereby preventing an accurate measurement. In order to stabilize the rotational speed, it requires a complicated control circuit that performs a feedback control by providing means for detecting number of revolutions such as a photo interrupter, and means for regulating the supply voltage.
In the case of adopting an A.C. motor for the driving source, it is easier to stabilize the rotational speed than a D.C. motor under the condition of relatively steady frequency as with the commercial power supply. However, it also raises a problem of necessitating an A.C. power supply such as the commercial power supply. Since a portable radiation thermometer operated by a battery source has only a D.C. power supply, it needs a complicated circuit for generating an A.C. power supply having a steady frequency, which is difficult to realize.
In the case of adopting a crystal clock movement or a pulse motor for the driving source, it is able to switch the light-admitting mode and the light-blocking mode at highly accurate intervals, since they are driven on the basis of digital signals from a microprocessor, etc. There is still a problem, however, that it is difficult to accurately switch between the light-admitting position and the light-blocking position, because the chopper stops while staggering. In other words, since these driving sources stop in an equilibration between an attractive force and a repulsive force of the magnets, and drive by changing polarities of the magnetic force, they have a characteristic of coming to rest by taking a balance between the attractive force and the repulsive force while the chopper is staggering at a moment of stopping.
FIGS. 30A and 30B show a characteristic of a motion of the pulse motor with an elapsed time in the horizontal axis. FIG. 30A depicts driving pulses of CW (clockwise direction) and CCW (counterclockwise direction), which are output alternatively at a predetermined interval of xe2x80x9ctxe2x80x9d with a duty factor of 50%. FIG. 30B depicts rotational angle of a rotary shaft of the pulse motor. As shown, the rotary shaft overshoots at a point of reaching the stop position, undershoots thereafter, and comes to rest at the stop position while gradually decreasing its amplitude.
Since the pulse motor and the crystal clock movement generally have the moving characteristic as shown in FIGS. 30A and 30B, they pose a problem of lacking measuring accuracy, if they are used as a driving source of the chopper for interrupting the infrared rays in a radiation thermometer. This is because they produce a condition of switching the infrared rays between a light-admitting mode and a light-blocking mode in very short intervals at a moment when the chopper moves from the light-admitting position to the light-blocking position, or from the light-blocking position to the light-admitting position, which causes an output of the infrared-ray-receiving element unstable. Although this problem can be alleviated by way of adopting a chopper having a size large enough for a maximum angle xcex94xcex8 of the staggering, it raises another problem of causing the body of the radiation thermometer to be bulkier in size.
A radiation thermometer of the present invention comprises (1) a light receptor for receiving only the infrared rays radiated directly from the eardrum and/or vicinity of it, (2) a signal processor for calculating a temperature from an output of the light receptor, and (3) notification means for notifying an output of the signal processor.
Since the thermometer calculates with the signal processor a temperature from the output of the light receptor, which receives only the infrared rays radiated directly from the eardrum and/or vicinity of it, and notifies the output with the notification means, it is able to detect the eardrum temperature accurately without getting an influence of other radiant heats than those of the eardrum and/or vicinity of it.
Also, a radiation thermometer comprises (1) a probe to be inserted into the ear canal for allowing the infrared rays radiated from the eardrum and/or vicinity of it to pass through, (2) a light receptor for receiving the infrared rays passed through the probe, (3) a signal processor for calculating a temperature from an output of the light receptor, and (4) notification means for notifying an output of the signal processor. The light receptor comprises at least an optical condenser for condensing the infrared rays passed through the probe, and an infrared-ray-receiving element positioned in a manner to receive only the infrared rays radiated from the eardrum and/or vicinity of it upon meeting the infrared rays condensed by the optical condenser.
The light receptor then receives only the infrared rays radiated from the eardrum and/or vicinity of it and passes through the probe. The signal processor converts the output of the light receptor into a temperature, and the notification means notifies the temperature resulted by the calculation. Since the infrared rays condensed by the optical condenser enters into the infrared-ray-receiving element in the light receptor, and the infrared-ray-receiving element is positioned in a manner to receive only the infrared rays radiated directly from the eardrum and/or vicinity of it upon meeting the infrared rays condensed by the optical condenser, it is able to concentratively detect only the light radiated from the eardrum and/or vicinity of it and passes through the probe, thereby resulting in an accurate temperature measurement.
The radiation thermometer is also constructed in manner that the infrared-ray-receiving element is positioned away in the rearward from a focal point of the optical condenser, so as to limit a light-receiving region. This enables the infrared-ray-receiving element to concentratively receive only the infrared rays radiated from the eardrum and/or vicinity of it and passes through the probe, and to limit the light-receiving region by directing the infrared rays radiated from an inner surface of the probe toward the outside of the infrared-ray-receiving element.
Also, the radiation thermometer comprises a main body for storing the light receptor, and a probe having a hollow interior, which is connected to the main body detachably. The light receptor stored in the main body receives only the infrared rays radiated from the eardrum and/or vicinity of it and passes through the probe. Since the probe with the hollow interior does not contain a waveguide, and is detachably connected to the main body, the thermometer does not lose accuracy in measured temperature due to temperature change of the waveguide. The thermometer does not pose a sanitary problem because the probe is replaceable, and it is easy to store since there is no protruding part when the probe is removed.
Further, the probe is provided with an opening at the tip so as to improve accuracy in measured temperature, since there is avoidance of temperature deviations due to dispersion of infrared transmittancy as in the case of using a cover overlaying the probe tip.
Moreover, the main body is provided with a storage space for storing the probe when the thermometer is not in use. Since the probe is stored in the storage space while not in use, the main body can be in a shape that is easy to store, and there is less likeliness of losing the removed probe.
There is a plurality of probes differently formed in a manner that individual probe is visually distinguishable. Since the visually distinguishable plurality of probes is provided, each probe can be specifically assigned to an individual user, and the problem of spread of disease via the ear can be prevented by replacing them.
Furthermore, the thermometer has a structure in which the notification means comprises a vocal announcing device for notifying a temperature result from calculation by the signal processor. The thermometer can measure accurate body temperature irrespective of the length of time while it is inserted in the ear.
The light receptor is equipped with a light-proof body for shielding the infrared rays entering into the infrared-ray-receiving element from an outside of the optical condenser, and a reflection suppressing means at the infrared-ray-receiving element side of the light-proof body. This structure prevents the infrared rays traveling toward an area other than the infrared-ray-receiving element from entering into the infrared-ray-receiving element due to reflection. The structure thus restricts a light-receiving region, and concentrates the infrared rays emitted from any part other the eardrum and/or vicinity of it to the outside of the infrared-ray-receiving element, thereby attaining an accurate measurement of the body temperature without being influenced by temperature change of the probe.
A synthetic resin is used for material of the light-proof body. The light-proof body made of the synthetic resin can suppress reflection, since it is well known that synthetic resin generally has a high value of emissivity in the neighborhood of 0.9. Also condensation is not likely to occur on a surface of the light-proof body, since synthetic resin has a low thermal conductivity and a small thermal capacity. Accordingly, the thermometer can measure accurate body temperature without causing reflection and scattering of the infrared rays due to condensation.
Since the optical condenser is composed of a material having a low thermal conductivity and a small thermal capacity, a waveguide for shielding the infrared rays from the probe is not necessary, and the optical system including the optical condenser need not have a high thermal conductivity. Because the optical condenser is composed of a material having a low thermal conductivity and small thermal capacity, condensation is not likely to occur on a surface of the optical condenser, so that the thermometer is able to measure accurate body temperature.
A synthetic resin is used for material of the optical condenser. Since synthetic resin generally has a low thermal conductivity and a small thermal capacity, as it is well known, it can reduce condensation on the surface of the optical condenser.
Also, a thermometer has a structure that an infrared-ray-receiving element is positioned in a region that is farther away from an optical condenser than an intersection between a light path and the optical axis, but nearer to the optical condenser than an image point of a hypothetical end point formed by the optical condenser, when viewed in a cross sectional plane including the optical axis of the optical condenser, where the light path is a path that extends from the hypothetical end point to the image point of the hypothetical end point formed by the optical condenser by passing through a rim of the optical condenser on the same side as the hypothetical end point with respect to the optical axis, and that the hypothetical end point is a point at which a straight line drawn from the rim of the optical condenser toward the probe in a manner to be tangent to an inner wall of the probe on the same side as the rim of the optical condenser with respect to the optical axis crosses a plane at a tip of the probe.
With this structure, the infrared rays incident upon the optical condenser from the inner surface of the probe can be directed to the outside of the infrared-ray-receiving element, so as to limit the light-receiving region. As a result, the thermometer is able to concentratively detect only the infrared rays radiated from the eardrum and/or vicinity of it and passes through the probe.
Further, a thermometer has a structure that an infrared-ray-receiving element is positioned within a triangle configured by an intersection between a light path and an optical axis, and two image points of a hypothetical end points formed by an optical condenser, when viewed in a cross sectional plane including the optical axis of the optical condenser, where the light path is a path that extends from the hypothetical end point to the image point of the hypothetical end point formed by the optical condenser by passing through a rim of the optical condenser on the same side as the hypothetical end point with respect to the optical axis, and that the hypothetical end point is a point at which a straight line drawn from the rim of the optical condenser toward the probe in a manner to be tangent to an inner surface of the probe on the same side as the rim of the optical condenser with respect to the optical axis crosses a plane at a tip of the probe.
By adopting this structure, the infrared rays incident upon the optical condenser from the inner surface of the probe can be directed to the outside of the infrared-ray-receiving element, so as to limit the light-receiving region. As a result, the thermometer is able to concentratively detect only the infrared rays radiated from the eardrum and/or vicinity of it and passes through the probe.
Furthermore, a thermometer has a structure that an infrared-ray-receiving element is positioned farther away from an optical condenser than a focal point of the optical condenser by a distance of L3, which is derived from the formula below, when viewed in a cross sectional plane including the optical axis of the optical condenser.                     f        xc3x97        f                              L          ⁢                      xe2x80x83                    ⁢          α                -        f              -                  f                              L            ⁢                          xe2x80x83                        ⁢            α                    -          f                    xc3x97                        L          ⁢                      xe2x80x83                    ⁢          α          xc3x97                      (                                          r                ⁢                                  xe2x80x83                                ⁢                                  α                  ·                  f                                            -                              rs                ⁢                                  (                                                            L                      ⁢                                              xe2x80x83                                            ⁢                      α                                        -                    f                                    )                                                      )                                                r3            xc3x97                          (                                                L                  ⁢                                      xe2x80x83                                    ⁢                  α                                -                f                            )                                +                      r            ⁢                          xe2x80x83                        ⁢                          α              ·              f                                             less than   L3  ≦            f      xc3x97      f                      L        ⁢                  xe2x80x83                ⁢        α            -      f      
where:
f is a focal distance of the optical condenser;
rs is a radius of the infrared-ray-receiving element;
rxcex1 is a distance between a hypothetical end point and the optical axis, where the hypothetical end point is a point at which a straight line drawn from the rim of the optical condenser toward the probe in a manner to be tangent to an inner surface of the probe on the same side as the rim of the optical condenser with respect to the optical axis crosses a plane at a top of the probe;
Lxcex1 is a distance between the hypothetical end point and the optical condenser; and
r3 is a radius of the optical condenser.
With this structure, the infrared rays incident upon the optical condenser from the inner surface of the probe can be directed to the outside of the infrared-ray-receiving element, so as to limit the light-receiving region. As a result, the thermometer is able to concentratively detect only the infrared rays radiated from the eardrum and/or vicinity of it and passes through the probe.
Moreover, a thermometer has a structure that an infrared-ray-receiving element is positioned in a region that is farther away from an optical condenser than an image point of a hypothetical end point formed by the optical condenser, when viewed in a cross sectional plane including the optical axis of the optical condenser, where the hypothetical end point is a point at which a straight line drawn from the rim of the optical condenser toward the probe in a manner to be tangent to an inner surface of the probe on the same side as the rim of the optical condenser with respect to the optical axis crosses a plane of the probe tip. With this structure, the infrared rays incident upon the optical condenser from the inner surface of the probe can be directed to the outside of the infrared-ray-receiving element, so as to limit the light-receiving region. As a result, the thermometer is able to concentratively detect only the infrared rays radiated from the eardrum and/or vicinity of it and passes through the probe.
Also, a thermometer has a structure that an infrared-ray-receiving element is positioned in a region lying between two light paths that extend from hypothetical end points to image points of the hypothetical end points formed by an optical condenser by passing through rims of the optical condenser on the opposite side of the hypothetical end point with respect to the optical axis, when viewed in a cross sectional plane including the optical axis of the optical condenser, where the hypothetical end point is a point at which a straight line drawn from the rim of the optical condenser toward the probe in a manner to be tangent to an inner surface of the probe on the same side as the rim of the optical condenser with respect to the optical axis crosses a plane at a tip of the probe.
By adopting this structure, the infrared rays incident upon the optical condenser from the inner surface of the probe can be directed to the outside of the infrared-ray-receiving element, so as to limit the light-receiving region. As a result, the thermometer is able to concentratively detect only the infrared rays radiated from the eardrum and/or vicinity of it and passed through the probe.
And further, a thermometer has a structure that an infrared-ray-receiving element is positioned farther away from an optical condenser than a focal point of the optical condenser by a distance of L3, which is derived from the formula below, when viewed in a cross sectional plane including the optical axis of the optical condenser.             f      xc3x97      f                      L        ⁢                  xe2x80x83                ⁢        α            -      f        ≦  L3   less than                     f        xc3x97        f                              L          ⁢                      xe2x80x83                    ⁢          α                -        f              +                  f                              L            ⁢                          xe2x80x83                        ⁢            α                    -          f                    xc3x97                        L          ⁢                      xe2x80x83                    ⁢          α          xc3x97                      (                                          r                ⁢                                  xe2x80x83                                ⁢                                  α                  ·                  f                                            -                              rs                ⁢                                  (                                                            L                      ⁢                                              xe2x80x83                                            ⁢                      α                                        -                    f                                    )                                                      )                                                r3            xc3x97                          (                                                L                  ⁢                                      xe2x80x83                                    ⁢                  α                                -                f                            )                                -                      r            ⁢                          xe2x80x83                        ⁢                          α              ·              f                                          
where:
f is a focal distance of the optical condenser;
rs is a radius of the infrared-ray-receiving element;
rxcex1 is a distance between a hypothetical end point and the optical axis, where the hypothetical end point is a point at which a straight line drawn from the rim of the optical condenser toward the probe in a manner to be tangent to an inner surface of the probe on the same side as the rim of the optical condenser with respect to the optical axis crosses a plane at a tip of the probe,;
Lxcex1 is a distance between the hypothetical end point and the optical condenser; and
r3 is a radius of the optical condenser.
With this structure, the infrared rays incident upon the optical condenser from the inner surface of the probe can be directed to the outside of the infrared-ray-receiving element, so as to limit the light-receiving region. As a result, the thermometer is able to concentratively detect only the infrared rays radiated from the eardrum and/or vicinity of it and passes through the probe.
The optical condenser comprises a refractive lens, so that the infrared rays condensed by the refractive lens enter upon the infrared-ray-receiving element.
The optical condenser also comprises a condensing mirror, so that the infrared rays condensed by the condensing mirror enter upon the infrared-ray-receiving element.
The condensing mirror deflects a first optical axis incident upon the condensing mirror into a second optical axis exiting from the condensing mirror and entering into the infrared-ray-receiving element. Therefore, if the probe and the main body are formed to have a bent angle in consideration of handiness of the radiation thermometer, as it is used by inserting into the ear canal, the optical system can be bent also in the same angle. As a result, the thermometer becomes convenient to use, and it can provide an accurate measurement of the body temperature since a direction of insertion becomes consistent because it is easy to insert into the ear canal.
A radiation thermometer also comprises (1) an infrared-ray-receiving element for detecting the infrared rays radiated by a subject being measured, (2) a chopper for interrupting the infrared rays incident upon the infrared-ray-receiving element, (3) a D.C. motor for driving the chopper, (4) a stopper provided at a stopping position of the chopper, (5) a motor controller for controlling the D.C. motor, and (6) a signal processor for converting an output of the infrared-ray-receiving element into a temperature. The motor controller controls a light-admitting mode and a light-blocking mode for the infrared rays travelling through the infrared-ray-receiving element by alternately reversing a rotational direction of the D.C. motor.
The chopper driven by the D.C. motor stops at each of a light-admitting position and a light-blocking position in a path of the infrared rays from the subject being measured to the infrared-ray-receiving element by striking against the stopper provided at the stopping position. A light-admitting time and a light-blocking time are steadily controlled by way of driving the chopper, since the motor controller switches between the light-admitting mode and the light-blocking mode by alternately reversing the rotational direction of the D.C. motor, and the signal processor converts into a temperature of the subject being measured based on an output of the infrared-ray-receiving element. Also, the chopper can switch steadily between the light-admitting position and the light-blocking position even if it is substantially reduced in size, since it does not stagger at its stopping position, thereby attaining highly accurate measurement of the body temperature with the reduced size.
Further, the intervals for alternately reversing the rotational direction of the D.C. motor are set to be longer than a responding time constant of the infrared-ray-receiving element, so that the infrared-ray-receiving element produces a high output and improves an S/N ratio, resulting in improved measuring accuracy of the body temperature.
The motor controller supplies electric power to the D.C. motor based on a predetermined power supply pattern. The D.C. motor is thus controlled according to the predetermined power supply pattern, so as to switch the infrared rays between the light-admitting mode and the light-blocking mode with the chopper.
The power supply pattern comprises a positive power supply pattern for supplying the power in a direction of the light-admitting mode, and a negative power supply pattern for supplying the power in a direction opposite to the light-admitting mode, and it constitutes a positive/negative power supply pattern for alternately repeating the positive and the negative power supply patterns. With the alternate supplies of the positive power supply pattern and the negative power supply pattern, the D.C. motor is able to reverse the rotational direction alternately.
The positive/negative power supply pattern consists of an initial power supply period for supplying the power at the start, and a reduced power supply period for supplying a reduced power thereafter. An initial supply of the power moves the chopper to a position of the stopper, and subsequent supply of the reduced power keeps the chopper in that position, thereby reducing the power consumption.
Also, by adopting an intermittent supply of the power during the reduced power supply period, the power consumption can be reduced, and the circuit structure can be simplified.
By ceasing supply of the power during the reduced power supply period, the power consumption can be farther reduced.
Furthermore, the power is supplied momentarily at a very end of the reduced power supply period after a period of the ceased power. Since this pattern reverses the D.C. motor after restriking the chopper against the stopper, it reduces the power consumption with a simple circuit structure, and precisely maintains the light-admitting time and the light-blocking time of the infrared rays to the infrared-ray-receiving element, thereby enabling an accurate measurement of the body temperature.
The initial power supply period is set to be longer than the sum of a time required for the chopper to reach the stopper and a time required for the chopper to make a complete stop after bouncing back from the stopper. An initial power supply unit supplies the D.C. motor with the initial power during the initial power supply period, which is longer than the sum of the time required for the chopper to reach the stopper and the time required to make a complete stop after bouncing back from the stopper, and the reduced power thereafter, so that the chopper stops reliably at the stopper position, and stably switches between the light-admitting position and the light-blocking position, thereby improving the measuring accuracy of body temperature while also reducing the power consumption.
Since the stopper is composed of a shock absorbing material, it stabilizes the chopping by alleviating the chopper from cutting into it or bouncing back, thereby resulting in an improvement of the measuring accuracy of body temperature as well as a reduction of sound caused by the chopper striking the stopper.
Also, the stopper is composed of a soft rubber material, it stabilizes the chopping by alleviating the chopper from cutting into it or bouncing back, so as to improve the measuring accuracy of body temperature as well as a reduction of sound caused by the chopper striking the stopper.
A view restricting means is provided between the infrared-ray-receiving element and the chopper for limiting a field of view for the infrared-ray-receiving element, and the chopper is constructed in a size greater than the field of view for the infrared-ray-receiving element in the chopping position. The chopper can be reduced in size by limiting the field of view for the infrared-ray-receiving element. Since the chopper is constructed in a size greater than the field of view for the infrared-ray-receiving element in the light-blocking position, a difference in the output of the infrared-ray-receiving element between the light-admitting position and the light-blocking position becomes greater, so as to improve an accuracy in measuring the body temperature.
The view restricting means is composed of a material having low reflectivity on at least one surface facing toward the infrared-ray-receiving element in order to suppress reflection of the infrared rays from the view restricting means. This eliminates the infrared rays reflected off the view restricting means to enter into the infrared-ray-receiving element, and positively restricts the field of view for the infrared-ray-receiving element, so as to enable highly accurate measurement of the body temperature with a reduced size.
The stopper is provided in a position, in which a moving angle of the chopper from a rest position in the light-blocking mode to a next position where the light begins to be admitted becomes equal to a moving angle of the chopper from a rest position in the light-admitting mode to another position where the light begins to be blocked. The motor controller outputs signals at regular intervals for alternately reversing the rotational direction of the D.C. motor.
Accordingly, the light-admitting time and the light-blocking time for the infrared rays due to a motion of the chopper become equal, thereby obtaining a high output from the infrared-ray-receiving element, and highly accurate measurement of the body temperature.
The signal processor includes a Fourier transform device for calculating a signal component in a frequency equal to the frequency, with which the rotational direction of the D.C. motor is reversed alternately, from an output signal of the infrared-ray-receiving element by way of the discrete Fourier transform processing. A temperature of the subject being measured is converted according to an output of the Fourier transform device.
Accordingly, noise content other than the signal can be removed, and an accurate measurement of the body temperature can be taken, since the harmonics noise component of high degrees, which is not completely suppressible by the discrete Fourier transform processing, is scarcely generated because the light-admitting time and the light-blocking time are equal.
The motor controller comprises (1) a position aligning driver for aligning a position of the chopper by driving the D.C. motor, (2) a temperature detecting driver for measuring body temperature while switching a path of the infrared rays to the infrared-ray-receiving element between a light-admitting mode and a light-blocking mode by alternately reversing a rotational direction of the D.C. motor, and (3) a switching device for switching the position aligning driver and the temperature detecting driver. In this structure, the chopper is designed to stay in the same position at all times prior to a start of the measurements.
The position aligning driver aligns a position of the chopper by driving the D.C. motor and striking the chopper against the stopper. And, the temperature detecting driver switches between the light-admitting mode and the light-blocking mode for the path of the infrared rays through the infrared-ray-receiving element by striking and stopping the chopper against the stopper by reversing the rotational direction of the D.C. motor alternately. The switching device switches between the position aligning driver and the temperature detecting driver. Accordingly, the chopper is always maintained in the same position prior to a start of the measurements with the foregoing positional alignment of the chopper. This can stabilize the light-admitting time and the light-blocking time by a motion of the chopper during measurement of the body temperature, thereby attaining an accurate temperature measurement.
The thermometer is also provided with a signaling device for dispatching a temperature detection starting signal, and the motor controller has a clock for counting a lapse of time in which a temperature detection starting signal is not received from the signaling device. The switching device operates the temperature detecting driver when it receives a temperature detection starting signal before the clock completes counting of a predetermined time. And, the switching device operates the position aligning driver first, and the temperature detecting driver thereafter, if it receives a temperature detection starting signal after the clock has counted the predetermined time.
Accordingly, the clock counts a lapse of time in which it does not receive a temperature detection starting signal from the signaling device, and the switching device operates the temperature detecting driver to measure the body temperature if it receives the temperature detection starting signal before the clock completes counting of the predetermined time. The switching device operates the position aligning driver first to align a position of the chopper, and switches to the temperature detecting driver to measure the body temperature, if it receives the temperature detection starting signal after the clock has completed counting of the predetermined time. In the case of taking measurements of body temperature repeatedly in a short period of time in which positional shift of the chopper from the last stopping position during the measurement is considered not likely, the measurement can be repeated continuously without executing the positional alignment of the chopper, so as to accomplish highly accurate measurements within a short period of time. Also, even if the chopper has shifted its position while the thermometer has been put aside without being used for a long period of time, accurate measurements can still be accomplished at all the time, since the measurements of body temperature is made only after executing a positional alignment of the chopper when resuming the measurement.
The thermometer is provided with a signaling device for dispatching a temperature detection starting signal. The switching device operates the position aligning driver when the power supply is turned on to the motor controller, and also the temperature detecting driver when it receives a temperature detection starting signal from the signaling device.
The switching device executes a positional alignment of the chopper by operating the position aligning driver when the power supply to the motor controller is turned on, and measures the body temperature by operating the temperature detecting driver when it receives the temperature detection starting signal from the signaling device. Hence, the thermometer can accomplish highly accurate measurements efficiently within a short period of time, when taking measurements repeatedly in short intervals.
The thermometer is provided with a power supply controller for turning on and off of the power supply to the motor controller. Also the power supply controller has a clock for counting a lapse of time during which a temperature detection starting signal is not received from the signaling device, and it turns off the power supply when the clock completes counting of a predetermined time.
The clock counts a lapse of time in which it does not receive a temperature detection starting signal from the signaling device, and the power supply controller turns off the power supply to the motor controller when the clock completes counting of the predetermined time. This necessitates the power supply to the motor controller to be turned on again, if taking a measurement thereafter. Accordingly, the measurements of body temperature can be made continuously without executing a positional alignment of the chopper, if repeated measurements are made in short intervals until the clock completes counting of the predetermined time, so that highly accurate measurements are accomplished in a short period of time. Also, the power supply to the motor controller is turned off when the clock completes counting of the predetermined time. The power supply to the motor controller needs to be turned on, when taking a measurement of body temperature again, and this causes the switching device to operate the position aligning driver for executing a positional alignment of the chopper. Therefore, even if the chopper has shifted its position while the thermometer has been put aside without being used for a long period of time, accurate measurements can still be accomplished at the time, since the measurements of body temperature is made with a subsequent temperature detection starting signal. The structure also reduces the power consumption and improves convenience of use, since the power supply to the motor controller turns off automatically after a lapse of the predetermined time even when the power supply is unintentionally left on.